Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Embedded hyperlinks in a thesis or research paper. Short story about swapping bodies as a job; the person who hires the main character misuses his body. Therefore, you need to change it to long long instead of long in windows for 64 bits. If the sizes are different then endianess comes into play. Find centralized, trusted content and collaborate around the technologies you use most. How to force Unity Editor/TestRunner to run at full speed when in background? Episode about a group who book passage on a space ship controlled by an AI, who turns out to be a human who can't leave his ship? And, most of these will not even work on gcc4. A good thing in general, but if you want to disable the warning, just do it. For example, (double) 1/3 will give a double result instead of an int one. This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s). Or keep using a C cast even when C++ code compiled as C++. If your code has the chance to ever be ported to some platform where this doesn't hold, this won't work. I don't see how anything bad can happen . [-Wextra-tokens] (if it doesn't, remove the -fno-diagnostics-show-option flag). If not, check the pointer size on your platform, define these typedefs accordingly yourself and use them. From the question I presume the OP does. The most general answer is - in no way. Instead of using a long cast, you should cast to size_t. What are the advantages of running a power tool on 240 V vs 120 V? Asking for help, clarification, or responding to other answers. Convert integers, floating-point values and enum types to enum types. The code ((void*)ptr + 1) does not work, because the compiler has no idea what size "void" is, and therefore doesn't know how many bytes to add. The error message mentions the diagnostic responsible for error message, e.g. Were sorry. For more information, see How to convert a byte array to an int, How to convert a string to a number, and How to convert between hexadecimal strings and numeric types. Integer conversions, both implicit and explicit (using a cast), must be guaranteed not to result in lost or misinterpreted data. You can then disable this diagnostic completely by adding -Wno-extra-tokens (again, the "extra tokens" warning is an example), or turn it into a non-fatal warning by means of -Wno-error=extra-tokens. cast to void *' from smaller integer type 'int cast to void *' from smaller integer type 'int. I get the error: "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha(residents[i].name) == 0), How a top-ranked engineering school reimagined CS curriculum (Ep. You cannot just cast the 32-bit variable to a pointer, because that pointer on a 64-bit machine is twice as long. In C#, you can perform the following kinds of conversions: Implicit conversions: No special syntax is required because the conversion always succeeds and no data will be lost. this question. Did the drapes in old theatres actually say "ASBESTOS" on them? You need to cast the void* pointer to a char* pointer - and then dereference that char* pointer to give you the char that it points to! Canadian of Polish descent travel to Poland with Canadian passport. Join Bytes to post your question to a community of 472,246 software developers and data experts. what does it mean to convert int to void* or vice versa? ERROR: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int', error: cast to 'string' (aka 'char *') from smaller integer type 'int' [-Werror,-Wint-to-pointer-cast], error: incompatible integer to pointer conversion assigning to 'string' (aka 'char *') from 'int' C, warning: initialization of 'unsigned char' from 'uint8_t *' {aka 'unsigned char *'} makes integer from pointer without a cast [-Wint-conversion], Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. pointer/reference to a derived class pointer/reference. MIP Model with relaxed integer constraints takes longer to solve than normal model, why? There are two occurences in "SemaCast.cpp" -- one of which suggests it's sensitive to MS extensions, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112 Surely the solution is to change the type of ids from int to type that is sufficiently large to hold a pointer. I'm not sure how to tell Clang (it's tools, really) that the platform is a 32-bit platform and to stop complaining. In 64-bit programs, the size of the pointer is 64 bits, and cannot be put into the int type, which remains 32-bit in almost all systems. You are right! Ubuntu won't accept my choice of password, Adding EV Charger (100A) in secondary panel (100A) fed off main (200A), Passing negative parameters to a wolframscript. Why did DOS-based Windows require HIMEM.SYS to boot? What is the correct method to cast an int to a void*? However, you are also casting the result of this operation to (void*). Or you might need to assign a class variable to a variable of an interface type. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You could use this code, and it would do the same thing as casting ptr to (char*). equal to the original pointer: First you are using a define, which is not a variable. For the second example you can make sure that sizeof (int) <= sizeof (void *) by using a static_assert -- this way at least you'll get a notice about it. You are just making it bigger by tricking the compiler and the ABI. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. I'm new to coding and am trying to implement a simple program on my own, that prompts the user the number of residents in an apt complex, the prompts the user to enter the names and apt numbers of each resident. Generating points along line with specifying the origin of point generation in QGIS. I need to convert the argument to an int for later use: The compiler (GCC version 4.2.4) returns the error: You can cast it to an intptr_t type. Converting a void* to an int is non-portable way that may work or may not! As was pointed out by Martin, this presumes that sizeof(void*)>=sizeof(int). Generating points along line with specifying the origin of point generation in QGIS. Using an integer address (like &x) is probably wrong, indeed each modification you will execute on x will affect the pass behaviour. @DavidHeffernan I rephrased that sentence a little. If the data types are compatible, then Java will perform the conversion automatically known as Automatic Type Conversion, and if not then they need to be cast or converted explicitly. Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? Is a downhill scooter lighter than a downhill MTB with same performance? "Signpost" puzzle from Tatham's collection. Unfortunately, that hardware is 64-bit and the code contains many instances of pointer arithmetic that expects pointers to be 32-bit, i.e. This forum has migrated to Microsoft Q&A. The point is (probably) that the value passed to the thread is an integer value, not really a 'void *'. Question is, how do I explain this to Clang? Explicit conversions (casts): Explicit conversions require a cast expression. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Using printf with a pointer to float gives an error, Meaning of int (*) (int *) = 5 (or any integer value), Casting int to void* loses precision, and what is the solution in required cases, Short story about swapping bodies as a job; the person who hires the main character misuses his body. You can use any other pointer, or you can use (size_t), which is 64 bits. You are getting warnings due to casting a void* to a type of a different size. it often does reinterpret_cast<uint32_t> (ptr). converted back to pointer to void, and the result will compare equal By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Passing arguments to pthread_create - invalid conversion from void(*)() to void(*)(void*). As a result, it is possible to silently convert from one pointer type to another without the compiler diagnosing the problem by storing or casting a pointer to void * and then storing or casting it to the final type. If you really need such trickery, then consider one of dedicated types, which are intptr_t and uintptr_t. The most general answer is in no way. On a 64-bit Windows computer, 'long' is a 32-bit type, and all pointers are 64-bit types. Usually that means the pointer is allocated with. Asking for help, clarification, or responding to other answers. I have a function with prototype void* myFcn(void* arg) which is used as the starting point for a pthread. If your standard library (even if it is not C99) happens to provide these types - use them. Losing bytes like thisis called 'truncation', and that's what the first warning is telling you. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, "what happen when typcating normal variable to void* or any pointer variable?" Thanks Jonathan, I was thinking about my answer in another thread: AraK is correct, passing integers a pointers are not necessarily interchangeable. For reference types, an explicit cast is required if you need to convert from a base type to a derived type: A cast operation between reference types does not change the run-time type of the underlying object; it only changes the type of the value that is being used as a reference to that object. So instead I modified the implementation of malloc to ensure it never allocates memory above the 4GB limit. Who has a solution to casting from int to void* and back to int, http://www.ungerhu.com/jxh/clc.welcome.txt, http://benpfaff.org/writings/clc/off-topic.html. OP said he doesn't want it. In both cases, converting the pointer to an integer type that's too small to represent all pointer values is a bug. pthread create managing values generated in function (in c), Establishing TCP socket connection between PHP client and C server on Ubuntu. For a complete list of supported explicit numeric conversions, see the Explicit numeric conversions section of the Built-in numeric conversions article. I saw on a couple of recent posts people saying that casting the return -1, Uggh. Thanks for contributing an answer to Stack Overflow! What is this brick with a round back and a stud on the side used for? how to cascade 2d int array to 2d void pointer array? Can anybody explain how to pass an integer to a function which receives (void * ) as a parameter? error: comparison between pointer and integer ('int' and 'string' (aka 'char *')), CS50 Caesar program is working but check50 says it isn't. A. if(x%2=1)y=x;B. if(sqrt(x)%2)y=x;C. if(x==1)y=x;D. if(x==1)y=&x; Cerror: cast to 'void *' from smaller integer type 'int'. What would you do next year when you need to port it to yet another experimental hardware? MIP Model with relaxed integer constraints takes longer to solve than normal model, why? I have the following function and when I compile it under VS.NET 2005, the following compile warnings show up: Warning1warning C4311: 'type cast' : pointer truncation from 'void *' to 'long'c:\temp\testone\lib\utils.c56Warning2warning C4312: 'type cast' : conversion from 'unsigned long' to 'void *' of greater sizec:\temp\testone\lib\utils.c56, Code Snippet And in this context, it is very very very common to see programmers lazily type cast the. For some type X he has: Thanks for contributing an answer to Stack Overflow! To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. property that any valid pointer to void can be converted to this type, Therefore, after you declare i as an int, you cannot assign the string "Hello" to it, as the following code shows: However, you might sometimes need to copy a value into a variable or method parameter of another type. and how to print the thread id of 2d array argument? The reinterpret_cast makes the int the size of a pointer and the warning will stop. this way you won't get any warning. How to get the error message from the error code returned by GetLastError()? I can easily imagine a situation where rewriting code using, Disabling "cast from pointer to smaller type uint32_t" error in Clang, https://github.com/llvm-mirror/clang/blob/release_50/include/clang/Basic/DiagnosticSemaKinds.td#L6193, https://github.com/llvm-mirror/clang/blob/release_50/lib/Sema/SemaCast.cpp#L2112, How a top-ranked engineering school reimagined CS curriculum (Ep. The only exception is exotic systems with the SILP64 data model, where the size of int is also 64 bits. I am an entry level C programmer. Since all pointers on 64-bit Windows are 64 bits, you are growing the data size from 32 bits backto 64 bits. I hit this same problem in a project without C++11, and worked around it like this: Thanks for contributing an answer to Stack Overflow! The content you requested has been removed. BUT converting a pointer to void* and back again is well supported (everywhere). Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Why did US v. Assange skip the court of appeal? Since the 'size' argument for your function is the number of bytes each element in the array needs, I think casting the pointerto (char*) is appropriate. How do I work around the GCC "error: cast from SourceLocation* to int loses precision" error when compiling cmockery.c? This is not a conversion at all. Use returnPtr[j] = (void *) ((long)ptr + i); ). for saving RAM), use union, and make sure, if the mem address is treated as an int only if you know it was last set as an int. For more information, see Polymorphism. X* px = new X; Note that it's not guaranteed that casting an, Generally this kind of type casting does not lead to any concern as long as the addresses are encoded using the same length as the "variable type" (. Thank you all for your feedback. Not the answer you're looking for? /** Dynamically allocate a 2d (x*y) array of elements of size _size_ bytes. If any, how can the original function works without errors if we just ignore the warning. Write values of different data types in sequence in memory? No special syntax is necessary because a derived class always contains all the members of a base class. Since the culprit is probably something like -Wall which enables many warnings you should keep on, you should selectively disable this single warning. Windows has 32 bit long only on 64 bit as well. To learn more, see our tips on writing great answers. Which reverse polarity protection is better and why? The error I'm getting is: error: cast from pointer to smaller type 'uint32_t' (aka 'unsigned int') loses information. How to use Clang static analyzer with a Cortex-M project? ', referring to the nuclear power plant in Ignalina, mean? The following program casts a double to an int. Which reverse polarity protection is better and why? There's no proper way to cast this to int in general case. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Many errors come from warnings. But, sure, in that specific case you can pass a local variable address, type casting integer to void* [duplicate]. Why did US v. Assange skip the court of appeal? this way I convert an int to a void* which is much better than converting a void* to an int. ), For those who are interested. It keeps throwing this exact error message even though both types are 32 bits wide. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? */void **MatrixIB (unsigned long x, unsigned long y, int size){ void *ptr; void **returnPtr; register unsigned long i, j; returnPtr = (void **) malloc (x * sizeof(void *)); ptr = (void *) malloc (x * y * size); for (i=0, j=0; j returnPtr[j] = (void *) (ptr + i); // <<< Compile Errors, Error1error C2036: 'void *' : unknown sizec:\temp\testone\lib\utils.c57, 2> returnPtr[j] = (void *) ((long*)ptr + i); // <<< No compile errors, 3> returnPtr[j] = (void *) ((char*)ptr + i); // <<< No compile errors. Should I re-do this cinched PEX connection? So, when you cast a (void*) to (long), you are losing 32 bits of data in the conversion. dynamic_cast safely converts pointers and references to classes up, down and sideways along the inheritance hierarchy - according to CppReference. is there such a thing as "right to be heard"? This is an old C callback mechanism so you can't change that. How should a standardized and beautiful flowchart be designed? The only. Please note that the error I am receiving is "cast to smaller integer type 'int' from 'string' (aka 'char *')" referencing line of code: while (isalpha (residents [i].name) == 0). This code is a bit odd (but a void* can certainly host a int on all architectures on which GDAL can be compiled), and certainly unused by anyone, so you could just remove the GetInternalHandle () implementation as well if you prefer. u32 -> u8) will truncate Casting from a smaller integer to a larger integer (e.g. This example is noncompliant on an implementation where pointers are 64 bits and unsigned integers are 32 bits because the result of converting the 64-bit ptr cannot be represented in the 32-bit integer type. Again, all of the answers above missed the point badly. There exist two main syntaxes for generic type-casting: functional and c-like: 1 2 3 4 double x = 10.3; int y; y = int (x); // functional notation y = (int) x; // c-like cast notation The functionality of these generic forms of type-casting is enough for most needs with fundamental data types. rev2023.5.1.43405. I personally upvoted this answer because by it's first line of text it helped me to understand the reason of this strange error message and what am I, poor idiot, doing :D. Not valid on Windows 64 - long is still 32-bit but pointers are 64-bit. rev2023.5.1.43405. (i.e. To learn more, see our tips on writing great answers. There is no "correct" way to store a 64-bit pointer in an 32-bit integer. d=(double *) Hi, LLNL's tutorial is bad and they should feel bad. He also rips off an arm to use as a sword. Did the drapes in old theatres actually say "ASBESTOS" on them? The main point is: a pointer has a platform dependent size. If you need to keep the returned address, just keep it as void*. even though the compiler doesn't know you only ever pass myFcn to pthread_create in conjunction with an integer. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Just edited. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Why did US v. Assange skip the court of appeal? last post by: I'm looking for the name of the following casting style in order to do By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use. If so, is Was Aristarchus the first to propose heliocentrism? Does it effect my blogs SEO rankings? static const void* M_OFFSET = (void*)64*1024; Since gcc compiles that you are performing arithmetic between void* and an int ( 1024 ). Is "I didn't think it was serious" usually a good defence against "duty to rescue"? There is absolutely not gurantee that sizeof(int) <= sizeof(void*). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Most answers just try to extract 32 useless bits out of the argument. The 32 remaining bits stored inside int are insufficient to reconstruct a pointer to the thread function. Why are players required to record the moves in World Championship Classical games? I'm trying to create a void* from an int. I don't understand why the following two cases produce different Hi, I've this question: suppose we have two differently typed pointers: If your standard library (even if it is not C99) happens to provide these types - use them. return ((void **) returnPtr);} /* Matrix() */. Can I use the spell Immovable Object to create a castle which floats above the clouds? Passing negative parameters to a wolframscript, Generating points along line with specifying the origin of point generation in QGIS. Keep in mind that thrArg should exist till the myFcn() uses it. My blogs h2 and other tags are in these manner. To perform a cast, specify the type that you are casting to in parentheses in front of the value or variable to be converted. Or, they are all wrong. I understood, but that would introduce dynamic memory and ugly lifetime issues (an object allocated by one thread must be freed by some other) - all just to pass an. So you could do this: Note: As sbi points out this would require a change on the OP call to create the thread. Did the drapes in old theatres actually say "ASBESTOS" on them? Canadian of Polish descent travel to Poland with Canadian passport. What I am trying to emphasis that conversion from int to pointer and back again can be frough with problems as you move from platform to platform. What does 'They're at four. Making statements based on opinion; back them up with references or personal experience. I agree that you should bite the bullet and fix the code to use the correct integer type. Nov 14 '05 or, Array with multiple data types? Where can I find a clear diagram of the SPECK algorithm? Connect and share knowledge within a single location that is structured and easy to search. The Test method has an Animal parameter, thus explicitly casting the argument a to a Reptile makes a dangerous assumption. There's no proper way to cast this to int in general case. But gcc always give me a warning, that i cannot cast an int to a void*. So,solution #3 works just fine. Even if you are compiling your program for a 32-bit computer, you should fix your code to remove these warnings, to ensure your code is easily portable to 64-bit. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. However, this specific error is not due to a warning and I can't find any option to disable errors (makes sense, since most errors are fatal). How to make compiler not show int to void pointer cast warnings, incompatible pointer types assigning to 'void (*)(void *)' from 'int (int *)'. I was sent this code and can't figure out why I keep getting "Incomplete Data type Error, Embracing Modern Android Development: A Dive into Java and Kotlin. For more information, see User-defined conversion operators. Asking for help, clarification, or responding to other answers. If we had a video livestream of a clock being sent to Mars, what would we see? You might want to typedef, You should change your code to handle this. Can I use my Coinbase address to receive bitcoin? Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey, error: cast from void* to int loses precision, cast to pointer from integer of different size, pthread code. For example, you might have an integer variable that you need to pass to a method whose parameter is typed as double. A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. Episode about a group who book passage on a space ship controlled by an AI, who turns out to be a human who can't leave his ship? I cannot reverse my upvote of user384706's answer, but it's wrong. Remembering to delete the pointer after use so that we don't leak. How can I control PNP and NPN transistors together from one pin? 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. Solution 1. The program will not compile without the cast. You can use any other pointer, or you can use (size_t), which is 64 bits. They should do their job unless your code is too tricky. void* -> integer -> void* rather than integer -> void* -> integer. I have a question about casting a function pointer. To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page. Not the answer you're looking for? is returned by the malloc. How do I check if a string represents a number (float or int)? If the null hypothesis is never really true, is there a point to using a statistical test without a priori power analysis? this way you won't get any warning. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. This is what the second warning is telling you. Your strategy will not work for stack-allocated objects, be careful!! To learn more, see our tips on writing great answers. Casting arguments inside the function is a lot safer. I think the solution 3> should be the correct one. Not the answer you're looking for? A cast is a way of explicitly informing the compiler that you intend to make the conversion and that you are aware that data loss might occur, or the cast may fail at run time. it means that myData is a variable of type "pointer to uint8_t", but it doesn't point to anything yet. Rep Power: 3. Why don't we use the 7805 for car phone chargers? Technically, these casts should therefore be valid. No sense in writing a few dozen lines of extra code just to get a bunch of numbered threads. And in the function you get the value of the pointer by using the dereference operator *: Please read why glib provide macros for this kind of conversions, there's no need to repeat the text here. C99 standard library provides intptr_t and uintptr_t typedefs, which are supposed to be used whenever the need to perform such a cast comes about. It's always a good practice to put your #define's in brackets to avoid such surprise. Infact I know several systems where that does not hold. " is pointer to interface, not interface" confusion, Cast from uint8_t pointer to uint32_t integer compilation error. While working with Threads in C, I'm facing the warning, "warning: cast to pointer from integer of different size". pcs leave before deros; chris banchero brother; tc dimension custom barrels; cast void pointer to char array. Thus as a result it may be less error prone to generate a pointer dynamcially and use that. Based on the design of this function, which modification is right. How can I control PNP and NPN transistors together from one pin? Once you manage to make this cast, then what?! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. You just need to suppress the warning, and this will do it: This may offend your sensibilities, but it's very short and has no race conditions (as you'd have if you used &i). Thanks for contributing an answer to Stack Overflow! How to convert a factor to integer\numeric without loss of information? I am compiling this program in linux gcc compiler.. Can I use an 11 watt LED bulb in a lamp rated for 8.6 watts maximum? The pointer doesn't actually point to anything, but it's the result of an earlier cast from an integer to a pointer (e.g. Which was the first Sci-Fi story to predict obnoxious "robo calls"? When is casting void pointer needed in C? Unless you have a valid address at that value, you are going to invoke undefined behaviour when try to use that pointer. If this is the data to a thread procedure, then you quite commonly want to pass by value. Definition: C++ introduced a different cast system from C that distinguishes the types of cast operations. Is it safe to publish research papers in cooperation with Russian academics? For built-in numeric types, an implicit conversion can be made when the value to be stored can fit into the variable without being truncated or rounded off. Referring to N1570 7.20.1.4/p1 (Integer types capable of holding object pointers): The following type designates a signed integer type with the property @ok 472,096 Members | 2,054 Online. Say you hack this successfully.

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